>> Are you using the expand global option? See tbl(1). That makes >> the table as wide as the line. > > No. It doesn't allow me to decide which column to stretch.
Then what about the `x' column specifier? (This is in groff 1.20.1.) x,X An expanded column. After computing all column widths without an x specifier, use the remaining line width for this column. If there is more than one expanded column, distribute the remaining horizontal space evenly among the affected columns (this is a GNU extension). This feature has the same effect as specifying a minimum column width. Werner